Servo - November 2015

a little too small. This may be remedied in the future, but for now — as long as I don’t roll it in a creek or let it go careening into a lake or pool — I should be fine.

The final touch was mounting the GoPro to the front.

With that, it was time to take it out.

Testing the Mantis took a couple of forms. First, I ran it around the neighborhood streets to get a feel for the handling and overall performance on flat ground. As expected, the 12V motors performed excellently with the

11.1V Li-Po battery. Acceleration was good and the torque from the planetary gears had no problems tackling any of the obstacles I put it up against. In fact, the wheels lost traction long before there was any issue with the motors stalling. There were a couple of times when the motors had a problem accelerating out of an obstacle, but once enough throttle was added it would power itself right through. However, the motors used with this kit are a known. I’ve used them with the Nomad and a couple other projects.

The real test was the chassis frame and suspension. In my little suburban trials, the sprung six-wheel suspension handled curbs and grass with no problem. Some adjustment was made to the front and rear springs to keep the chassis itself level while moving. When power was applied to the motors, the entire chassis wanted to lean backwards. This was not desirable when filming, so I increased the rear shocks and decreased the front. Now, it leans forward while at rest and is more or less level while traveling. Depending on future applications, I may add a pan-tilt mechanism for the camera. For these trials, however, a forward facing mount was sufficient and I wanted to keep it level during travel.

To further test the performance of the Mantis, I took it to a community park with plenty of nature trails and a couple creeks. Of course, with as little rain as we’ve had in the past few months, the creeks were either dry or stagnant. However, the banks were still steep, and the terrain was varied and dusty.

On the trail, the operation was smooth. Off the trail, it seemed unstoppable. Well, that is until “it” managed to get itself caught on a fallen branch. The stems got themselves hooked underneath the chassis on the motors, between the suspension arms, and the springs. This was not a big deal, but did take some work on the controls to free the bot, and some picking of stems and leaves out of joints later. After driving it through tall grass, I had to spend some time cutting grass from the wheel hubs and shaft adapters.

All of this is expected when running a robot off-road — where other robots fear to tread. None of the issues faced deterred the Mantis from doing exactly what it was told to